Rivet analyses

title: BABAR_2008_I782405

Mass distributions in $B^+\to K^+\pi^+\pi^-$

Experiment: BABAR (PEP-II)

Inspire ID: 782405

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 071103

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ mesons, originally Upsilon(4S) decays

Measurement of mass distributions in $B^+\to K^+\pi^+\pi^-$. The data were read from the figures in the paper and the backgrounds given subtracted.

Source code:BABAR_2008_I782405.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> K pi pi class BABAR_2008_I782405 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I782405);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(PID::K0S);
  declare(BP, "BP");
  // histos
  for (unsigned int iy = 0; iy < 3; ++iy) {
    book(_h_mass[iy], 1, 1, 1 + iy);
    for (unsigned int ix = 0; ix < 2; ++ix) book(_h_mass2[ix][iy], 2, 1 + iy, 1 + ix);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{321, 1}, {211, 1}, {-211, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {-211, 1}};
  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  // loop over particles
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    int sign = BP.decaying()[ix].pid() > 0 ? 1 : -1;
    if ((sign > 0 and BP.modeMatches(ix, 3, mode)) || (sign < 0 and BP.modeMatches(ix, 3, modeCC))) {
      LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
          BP.decaying()[ix].momentum().betaVec());
      // momenta
      FourMomentum pip = boost.transform(BP.decayProducts()[ix].at(211 * sign)[0].momentum());
      FourMomentum pim = boost.transform(BP.decayProducts()[ix].at(-211 * sign)[0].momentum());
      FourMomentum Kp = boost.transform(BP.decayProducts()[ix].at(321 * sign)[0].momentum());
      // mass distributions
      double mKpi = (Kp + pim).mass();
      double mpipi = (pip + pim).mass();
      // vetos
      if (mKpi > 1.756 && mKpi < 1.931) continue;
      if (mpipi > 1.660 && mpipi < 1.800) continue;
      if (mpipi > 3.019 && mpipi < 3.179) continue;
      if (mpipi > 3.627 && mpipi < 3.747) continue;
      // mass distributions
      if (mpipi > 2.) _h_mass[0]->fill(mKpi);
      if (mKpi > 2.) {
        _h_mass[1]->fill(mpipi);
        _h_mass[2]->fill(mpipi);
      }
      FourMomentum ppipi = pim + pip;
      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
      double cTheta = boost2.transform(pim).p3().unit().dot(Kp.p3().unit());
      _h_mass2[(sign + 1) / 2][0]->fill(mpipi);
      if (cTheta > 0)
        _h_mass2[(sign + 1) / 2][1]->fill(mpipi);
      else
        _h_mass2[(sign + 1) / 2][2]->fill(mpipi);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int iy = 0; iy < 3; ++iy) {
    normalize(_h_mass[iy], 1., false);
    for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h_mass2[ix][iy], 1., false);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[3], _h_mass2[2][3];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2008_I782405);

} ```